The recognized hazard of side collisions against towed trailers can be traced at least back to 1938 in which Robinson invented a peripheral guard for a hitch-mounted trailer. See U.S. Pat. No. 2,002,832. His patent teaches a fixed full periphery guard for a towed trailer with fixed rear axle. This non-adjustable system thus guarded against impacts to the trailer from all directions.
Page envisioned a more limited guard in U.S. Pat. No. 4,060,268. His device was designed for a large trailer with the front of the trailer attaching to a “fifth wheel” of the tractor vehicle. This articulated structure comprising prime-mover and towed load represents the consensus design for commercial cargo transport on U.S. highways today. In this concept, the compartmentalized cargo space is fully above the undercarriage. The weight of the transported goods is supported both by the trailer tires at the trailer's rear, and by the prime-mover's rear tires directly underneath the front of the trailer. The Page patent teaches a generally rectilinear rail guard and support system guarding the space between the prime-mover's rear tires and the trailer's rear-situated duals. The guard is adjustable for height but not length, such that sufficient clearance exists to prevent scraping of the guard against the roadway. This system does not contemplate a sliding rear axle system. It also does not address any geometric mismatch between a striking passenger vehicle and the region of the trailer behind the rear duals. Jacobs proposed a dynamic inflatable under-ride guard in the form of an exterior airbag and crash sensing system in U.S. Pat. No. 6,450,556. The purpose of this system is to absorb the impacting vehicle's kinetic energy and prevent under-ride, diminishing the hazard to the impacting vehicle. This patent teaches a plurality of systems, one for the rear, and at least one for each side between the trailer dual rear axles and the prime movers tires to the front of the trailer. Although a sliding rear axle system is envisioned by the inventor, no component of the system deals with the void space between the rearmost axial under-ride guard and the rear of the sliding undercarriage, and therefore the entirety of mismatch about the periphery of the trailer is not addressed.
Schroeder developed a fixed side guard system for sliding axle trailers which provided a conventional mechanical guard for the majority of the length of the trailer between the trailer tires and the prime mover tires. See U.S. Pat. No. 6,626,475. This system of rectangular bars is adjustable for the movement of the rear trailer suspension, but does not provide for side impact protection aft of the trailer tires when the rear undercarriage has been set in a position substantially forward of the rear under-ride guard. Unlike the Page-designed guard, the Schroeder guard was adjustable for axial length, but not height.
Goertz invented an energy absorbing rear under-ride guard that absorbed the kinetic energy of the impacting vehicle through guard rotation in U.S. Pat. No. 7,086,674. In this mechanism, the interacting guard rail is designed to pivot about an axle and resist the impacting force as it displaces from its rearmost position to a more forward position. Within the patent, Goertz describes how this rear guard can be adapted to the side locations forward of the trailer's undercarriage in discrete segments. Thus, the Goertz device does not include an adjustment mechanism and cannot fully address geometric mismatch if a sliding trailer axle is used.
Norelius designed a side impact guard for lorries (box trucks) which present similar impact hazards to passenger vehicles as do articulated trailers. See U.S. Pat. No. 7,188,875. The Norelius invention is adjustable for user access to the underside of the vehicle. In this invention, a stiff sheet unit mostly fills the void space between the lorry's steering tires to the front of the load bearing rear tires. The rectangular guard taught in the patent protects the occupants of impacting vehicles. One novel function described was the ability for the guard to rotate upwards and out of the way when access to the underside of the vehicle was desired. The lorry described in the preferred embodiment has no sliding axle capability, and thus no space behind the rear tires requiring guarding against transverse passenger vehicle impact.
Eriksson patented a conventional side guard for trucks that had the added functionality of acting as a support structure for aerodynamic fairings in U.S. Pat. No. 7,407,204. This non-adjustable guarding structure is for the region between the steer tires to the front and the drive tires to the rear, with no allowance for space behind the rearmost tires and forward of the rear impact guard.
Roush invented a crash attenuating under-ride guard that provided a three-dimensional complex aerodynamic surface structure, unlike the generally planar structures of previous inventions. See U.S. Pat. No. 7,780,224. An inherent function of this design is increased fuel efficiency. The invention incorporates a complex, sculptured surface and does not envision adjustability for a sliding rear axle assembly in any of the preferred embodiments.
Puppini developed a longitudinal impact system for trailers and semi-trailers by creating a novel storage container for spare tires that also provided protection for vehicles that impact the trailer laterally in U.S. Pat. No. 7,967,349. As many, perhaps nearly all, trailers carry spare tires pre-mounted on wheels, a component is already present which, through novel containerization, could provide a crashworthiness safety benefit. This system is not adjustable and provides a low weight penalty crashworthiness benefit. It does not address the impact hazard behind a towed trailer's sliding rear undercarriage.
Finally, in U.S. Pat. No. 8,162,384, Giromini teaches an adjustable side under-ride trailer system with cables, instead of the rigid guards and inflatable airbags taught previously. This design is energy absorbing, distributing the load of the impacting vehicle throughout all of the impacted cables. The invention also uses springs to increase the compliance of the cables thus providing a transverse-impact resistance function. In this design, no provision is made for the region between the rear under-ride guard and the rear of the trailer duals. If the trailer's rear-most tires are located forward from their rear-most position to provide a tire-load optimization, an un-addressed hazard is presented. The Giromini patent only protects the region forward of the trailer's rear undercarriage.